Category: Non-profit Organization

Replenishing Groundwater in the San Joaquin Valley

February 6, 2023 No Comments

The San Joaquin Valley—which has the biggest imbalance between groundwater pumping and replenishment in the state—is ground zero for implementing the 2014 Sustainable Groundwater Management Act (SGMA). Expanding groundwater recharge could help local water users bring their basins into balance and make a dent in the long-term deficit of nearly 2 million acre-feet per year.

The experience with recharge in 2017―the first wet year since the enactment of SGMA―offers valuable insights in how to expand recharge. A survey of valley water districts’ current recharge efforts revealed strong interest in the practice, and a number of constraints.

Groundwater Exchange website

February 6, 2023 No Comments

The Groundwater Exchange is a central, collaborative, and publicly accessible online resource center connecting water managers, water users, and community members with tools and resources to support the design and implementation of effective Groundwater Sustainability Plans under California’s Sustainable Groundwater Management Act. ​The Groundwater Exchange is a program of the California Water Library and is a project of the Multiplier, a 501(c)3 nonprofit organization that helps us protect and foster a healthy, sustainable, resilient, and equitable world.

Check out the “groundwater recharge” page (https://groundwaterexchange.org/groundwater-recharge/) for resources specific to Flood-MAR.

Introduction to Groundwater Recharge

February 6, 2023 No Comments

The Central Valley is one of the most productive agricultural regions in the United States. Growers and communities, however, are faced with a future of declining groundwater quality, quantity, and availability during drought, due to overdraft. In areas where soil conditions are suitable and excess water is available, ground water recharge represents one of the most cost-effective methods to increase storage, thereby ensuring water supply and improving water quality. Through this guide, California almond growers can begin evaluating their options for addressing local sub-basin overdraft through recharge, helping secure reliable, sufficient, and drought resilient groundwater supplies.

Multi-Benefit Recharge Project Methodology

February 6, 2023 No Comments

The Multi-Benefit Recharge Project Methodology Guidance Document summarizes considerations and planning that may go into designing, selecting, implementing, and monitoring a multi-benefit recharge project focused on creating suitable shorebird habitat. Projects should be customized to the specific settings and needs of each GSA in order to reach GSP sustainability goals and designed, selected, and implemented to maximize project benefits.

Building Multi-Benefit Recharge Basins

February 6, 2023 No Comments

As California faces an unpredictable water future, policy makers and water managers across the state are seeking solutions to build resilience into our water supply system. Groundwater recharge is an excellent tool to replenish depleted aquifers and bank water for future use. In addition to helping water managers balance their water budget, groundwater recharge also provides an opportunity to create habitat for wildlife. This guide highlights recharge basin management strategies that create wildlife habitat and provide operational benefits to basin managers.

Groundwater Resource Hub

February 2, 2023 No Comments

The purpose of the Groundwater Resource Hub is to help local agencies achieve sustainable groundwater management by providing the science and tools needed to help address nature’s water needs. Over time, the goal is to improve statewide and local understanding of nature’s groundwater needs to reduce uncertainties and therefore enhance sustainable groundwater management.

Groundwater dependent ecosystems (GDEs) are plant and animal communities that require groundwater to meet some or all of their water needs. California is home to a diverse range of GDEs including palm oases in the Sonoran Desert, hot springs in the Mojave Desert, seasonal wetlands in the Central Valley, perennial riparian forests along the Sacramento and San Joaquin rivers, and estuaries along the coast and in the Delta. These ecosystems rely on groundwater in California’s semi-arid climate, especially during dry summers and periods of drought. GDEs provide important benefits to California including habitat for animals, water supply, water purification, flood mitigation, erosion control, recreational opportunities and general enjoyment of California’s natural landscape.

Groundwater Dependent Ecosystems under the Sustainable Groundwater Management Act

February 2, 2023 No Comments

This guidance provides a systematic and defensible approach to identify GDEs, determine whether potential effects on GDEs are occurring or may occur due to groundwater conditions, and consider GDEs when setting sustainable management criteria. This guidance recommends setting sustainable management criteria based on the conditions necessary to avoid adverse impacts to GDEs and undesirable results in the basin, especially where conservation of species and habitats within GDEs is required by other laws, such as the Endangered Species Act.

This document is designed to inform local decision making, consistent with SGMA’s emphasis on local control. Rather than prescribing approaches or outcomes, this guidance provides a flexible process meant to enable GSAs and stakeholders to make decisions based on the best available science in a manner that promotes transparency and accountability.

Groundwater and Stream Interaction in California’s Central Valley: Insights for Sustainable Groundwater Management

February 2, 2023 No Comments

This report was undertaken to provide technical information on the state of streams and groundwater resources in the Central Valley. The findings of this report were used to support the need for what is now known as the Sustainable Groundwater Management Act (SGMA). The intent was to illustrate the physical inter-relationship between the surface and groundwater resources and the potential impacts that groundwater pumping has had and is currently having on our rivers and streams to demonstrate the need for sustainable groundwater management.

Based on the scale of the data used in this study, the findings contained herein should not be used as a definitive source in determining whether a particular stream or river reach should or should not be considered as an interconnected surface water for SGMA purposes. Further study at a finer scale would be necessary for such a determination.

ICONS: Interconnected Surface Water in California’s Central Valley

February 2, 2023 No Comments

Sustainable groundwater management in California requires an understanding of how groundwater pumping affects surface water features. Groundwater seeps into many river and lake beds in California, providing a steady source of cool clean water. This source of water is crucial for people and nature because it remains steady throughout the year even after the winter rains stop. Under the Sustainable Groundwater Management Act (SGMA),
interconnected surface water (ISW) is defined as “surface water that is hydraulically connected at any point by a continuous saturated zone to the underlying aquifer and the overlying surface water is not completely depleted” (Groundwater Sustainability Plan Emergency Regulations).

SGMA requires special treatment of ISW, but in many parts of the state, ISW is poorly understood. This dataset categories rivers and stream segments on the likelihood that they are ISW, using groundwater depth as a proxy to determine ISW. This data is available to view in an interactive online map at: http://icons.codefornature.org/.

Management Considerations for Protecting Groundwater Quality Under Agricultural Managed Aquifer Recharge

February 2, 2023 No Comments

Unsustainable groundwater use in California – due in large part to historical over-pumping of aquifer systems, growing reliance on groundwater to meet irrigation and urban water demands, and increasing frequency of drought – affects all water users and threatens agricultural viability into the future, but has disproportionately impacted disadvantaged communities and jeopardizes their access to safe, clean and affordable water. To secure the availability of groundwater for all uses, the state enacted the Sustainable Groundwater Management Act (SGMA) in 2014. Groundwater Sustainability Agencies (GSAs) were charged with developing Groundwater Sustainability Plans (GSPs) to avoid undesirable effects of ongoing groundwater depletion. To meet these goals, many GSPs include managed aquifer recharge (MAR) as one of several key tools to improve groundwater sustainability.

Agricultural Managed Aquifer Recharge (AgMAR) is the act of intentionally flooding fallow, dormant, or active cropland when excess surface water is available. AgMAR has the potential to be a cost-effective and high impact form of MAR due to the large acreage of cropland throughout California. As more farmers adopt AgMAR, there is greater urgency to understand the potential water quality risks and benefits associated with recharge. While pesticides and geogenic contaminants such as arsenic pose additional water quality concerns in MAR projects, this paper focuses specifically on water quality considerations for nitrate and salts related to AgMAR activities.

Nitrate contamination of groundwater is expected to worsen into the future. However, a combination of improved nutrient management and carefully implemented AgMAR projects could improve groundwater quality faster than under business as usual. Improvements in nitrogen management practices should be prioritized to reduce current and future nitrogen (N) loading to groundwater. Furthermore, relatively clean (nitrate free) recharge water (e.g. high magnitude flood flows) should be used during AgMAR events in order to dilute incoming and existing nitrate in groundwater. AgMAR programs should prioritize sites that can recharge in longer-duration single-flooding events, such as sandier sites, to capitalize on the dilution effect and reduce biologically mediated mineralization of organic N (the conversion of organic N to nitrate).

AgMAR alone will not lead to substantive improvement in groundwater quality with respect to nitrate without concomitant improvements in current agronomic nitrogen management and sufficient water for dilution. The development of transparent and easy-to-use tools that estimate the amount of residual nitrate at the end of a growing season, the amount of water needed to dilute nitrate under AgMAR, and time of travel to groundwater will help in the successful implementation of recharge projects to avoid negative water quality externalities. Current nitrogen loading maps and locations of drinking water supply wells can be used by GSAs to get a sense of regional nitrogen loading to groundwater and help in planning and prioritizing efforts on sites to target for AgMAR.